Hi Christopher! Christopher Baines <m...@cbaines.net> skribis:
> direnv [1] is an environment switcher for shells, for example, you want > to have a specific environment variable set when working on a particular > project, you drop a .envrc file in to the relevant directory and > providing direnv is hooked in to your shell, it will get loaded and > unloaded as you move in and out of that directory. > > 1: https://direnv.net/ > > While direnv is useful for simple environment variables, guix > environment can output environment variables with the --shell-paths > option. Using guix environment in a .envrc file would look something > like: > > eval "$(guix environment --ad-hoc guile --search-paths)" > > There is a use_guix helper function in the direnv stdlib [2] that helps > with this, so you can just do: > > use guix --ad-hoc guile This is pretty cool! However, using ‘guix environment --search-paths’ is kinda unsafe: the items mentioned in its output are not protected from GC. This is why ‘guix environment’ normally spawns a shell or some other process while keep its guix-daemon session open. > I've recently become aware of emacs-direnv [3], which provides access > to the functionality of direnv from Emacs. When the global minor mode > is active, this means that moving around between buffers in Emacs can > completely change the environment within Emacs. This had made my > workflow simpler, as I now just open Emacs, and navigate to the > relevant directory, and direnv just works behind the scenes. > > 3: https://github.com/wbolster/emacs-direnv I think it’d be great Emacs-Guix could do something similar, i.e., associate a ‘guix environment’ to a buffer. :-) > One issue with this is that running guix environment from direnv will > slow down switching buffers. To make it a bit more useable, I found > some bash code that caches the results of running commands, and wrapped > that around guix environment when invoked from direnv. This helps speed > things up, but I don't think its useful in the long term. > > For this particular use case, it would help if guix environment was > faster, perhaps by doing caching internally? On my system, running guix > environment --ad-hoc guile --search-paths repeatedly takes ~2 seconds, > I haven't looked at what the breakdown of this is yet. I agree that we could do a lot more things with a faster ‘guix environment’. My guess is that it won’t be easy to go optimize, and very hard to go below 1 second. We should profile that and see what can be done. Cheers, Ludo’.
